ferraus limit

True-peak brickwall limiter

Synopsis

ferraus limit <input> [options] [-o <output>]

Lookahead brickwall limiter that detects inter-sample peaks with oversampling, so the output never exceeds the ceiling when measured as true peak. The gain envelope ramps down over the lookahead window (no clicks) and recovers with the release time.

This command is also an fx stage and a pipeline op: ferraus fx in.wav -o out.wav --fx "limit:key=value".

Examples

Limit to -1 dBTP

ferraus limit mix.wav -o limited.wav

Hotter ceiling, slower release

ferraus limit master.wav --ceiling -0.3dBTP --release 100ms -o hot.wav

Leave extra headroom for lossy encoding (MP3 and AAC can add peaks)

ferraus limit podcast.wav --ceiling -2dBTP -o podcast_safe.wav

Fast sample-peak limiting with a short lookahead

ferraus limit drums.wav --ceiling -1dB --oversample 1x --lookahead 1ms -o drums_lim.wav

Options

Flag	Type	Default	Meaning
`--ceiling`	gain	`-1dBTP`	Maximum output level (true peak, dBTP)
`--release`	time	`50ms`	Recovery time after a peak
`--lookahead`	time	`5ms`	Attack ramp length (latency is compensated)
`--oversample`	1x \| 2x \| 4x \| 8x	`4x`	True-peak detection oversampling (1x = sample peak)
`--mix`	percent	`100%`	Dry/wet balance: 0% returns the input unchanged, 100% is fully processed

Global options

Every command also accepts the global options (-o, --json, --dry-run, --overwrite, --progress, ...). See Global options.

Exit codes

Code	Meaning
0	Success
1	Processing failed
2	Usage or parameter error
3	Input missing or unreadable
4	Unsupported format or codec
8	Cancelled
9	Output verification failed (checksum, clipping guard, duration mismatch)
70	Internal error (bug)

Common mistakes

Forgetting that outputs are never overwritten: pass --overwrite or a new -o path when re-running.
Beat-based times (4b, 1/4) need a tempo: pass --bpm or write 4b@120.
Gains need a unit when not in dB: 0.5x is a factor, -6 and -6dB are decibels.

For models

MCP tool: ferraus_limit
Schema: ferraus schema limit
Pipeline: { op: limit, args: { ... } } (flag names with _ instead of -)
fx stage: yes

{"command": "limit", "defaults": {"ceiling": "-1dBTP", "release": "50ms", "lookahead": "5ms", "oversample": "4x", "mix": "100%"}}